1. Field of the Invention
The present invention relates to a mobile telecommunication terminal, and more particularly, to an apparatus and method for controlling back lights in a liquid crystal display and a key pad for use in a mobile terminal.
2. Description of the Related Art
Recently, a portable personal telecommunication terminal is being commercially spread, which not only transmits input/output data with a microprocessor and a RAM without any assistance from a host computer, but also checks data, manages one""s schedule, and performs an electronic diary function under the control of its own program.
Such a portable personal telecommunication terminal includes a liquid crystal display for displaying more data, a key pad for inputting character and numeral data, and a flip cover for covering the liquid crystal display device and the key pad from external pollution sources.
With multi-functions of the portable personal telecommunication terminal, a function selection key is provided on either an outer side of the flip cover or a predetermined area of a main body not covered with the flip cover, so that telecommunication and a simple function can be performed and information can be input in even case that the flip cover is not open.
To facilitate use of the terminal at a dark place, a back light is provided at the rear of the key pad and the liquid crystal display. A light source is provided in the back light by a plurality of light-emitting diodes(LEDs).
An apparatus and method for controlling the back light in the aforementioned related art flip type mobile terminal will be described with reference to the accompanying drawings.
FIG. 1 is a block diagram showing a related art flip type mobile terminal and FIG. 2 is a flow chart showing a method for controlling a back light of the related art flip type mobile terminal.
As shown in FIG. 1, the related art flip type mobile terminal includes a liquid crystal display 30 for displaying data and information, a key pad 50 provided in a main body, for inputting character and numeral data, a flip switch 10 for detecting open and close state of a flip cover, first and second back lights 40 and 60 for providing a back light to the liquid crystal display 30 and the key pad 50, respectively, a function selection key 70 provided on an outer side of the flip cover or a predetermined area of the main body not covered with the flip cover, for selecting various functions in even case that the flip cover is not open, and a central processing unit (CPU) 20 for controlling the overall system of the mobile terminal and simultaneously driving the first and second back lights 40 and 60 in accordance with turn-on of the flip switch 10 or an input signal of the function selection key 70. The flip switch 10 is mechanically turned on/off by open and close state of the flip cover.
The method for controlling the back light in the aforementioned related art flip type mobile terminal will now be described with reference to FIG. 2.
As shown in FIG. 2, the CPU determines whether or not the function selection key 70 is turned on by a user (step S1). This is determined in such a manner that a signal selected by the user is applied to the CPU if the user pushes the function selection key 70.
If the function selection key 70 is turned on, the CPU simultaneously drives the first back light 40 of the liquid crystal display 30 and the second back light 60 of the key pad 50 (step S3).
However, if the function selection key is not pushed by the user, the CPU does not drive the first and second back lights so that the back lights are maintained turned off (step S4).
Also, the CPU determines whether or not the flip cover is opened by the user, through the flip switch 10 (step S2).
If it is determined that the flip cover is opened, the CPU simultaneously drives the first back light of the liquid crystal display and the second back light of the key pad 50 (step S3).
However, if the user does not open the flip cover, the CPU permits the first back light of the liquid crystal display 30 and the second back light of the key pad 50 to be turned off (step S4)
The back light of the liquid crystal display and the back light of the key pad are simultaneously driven or turned off by the control signal of the CPU.
The aforementioned apparatus and method for controlling a back light in the mobile terminal has several problems.
In even case that the user uses the function selection key formed on the outer side of the flip cover at the state that the flip cover is not open, the back light of the key pad is driven, thereby increasing power consumption. In addition, actual standby time of the mobile terminal is reduced due to unnecessary power consumption.
Accordingly, the present invention is directed to an apparatus and method for controlling a back light in a mobile terminal that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an apparatus and method for controlling a back light in a mobile terminal, in which a back light of a liquid crystal display and a back light of a key pad are independently controlled to reduce unnecessary power consumption.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an apparatus for controlling a back light in a mobile terminal according to the present invention includes a flip switch for detecting open and close state of a flip cover, a function selection key for being separately operated regardless of the open and close state of the flip cover, a first back light for supplying a light source to a liquid crystal display, a second back light for supplying a light source to a key pad, and a controller for driving the first and second back lights if the flip cover is opened and driving only the first back light if the function selection key is input.
In the preferred embodiment of the present invention, the controller includes a CPU for outputting a first back light enable signal B/L-EN in accordance with the flip switch and the function selection key, and an AND gate for driving the second back light by performing logic AND operation of the enable signal of the CPU and an output signal of the flip switch. The flip switch includes a first pin for supplying a constant voltage to a main board of the main body and a second pin connected to a ground terminal of the first pin. The flip switch is configured to electrically connect the first and second pins with each other if the flip cover is closed, and the function selection key is configured to electrically connect the first pin with the second pin at different resistance values in accordance with a key selected by a user.
In another aspect, a method for controlling a back light in a mobile terminal including a flip cover, a function selection key, a first back light of a liquid crystal display, and a second back light of a key pad, includes the steps of driving the first and second back lights if the flip cover is opened, and driving only the first back light if the function selection key is input.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.